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US 11,085,877 B2Granted
Apparatus and methods for measuring the refractive index of a fluid
AssigneeSchlumberger Technology Corporation
InventorsRicha Sharma, Raji Shankar, Terizhandur S. Ramakrishnan
Life of this patent
Estimating the term…
Abstract
Methods and apparatus are provided for determining the refractive index of a downhole fluid. Two unalike crystals are provided having faces in contact with fluid in the fluid flow line of a borehole tool. The crystals are chosen to have different refractive indices and/or different angles of incidence, but to provide total internal reflection for light that is directed through the crystals to the crystal/fluid interface. The measured attenuations for each crystal are used in conjunction with the known refractive indices and angles of incidence of said crystals to determine the refractive index of the fluid.
Claims12
A borehole apparatus for determining the refractive index of a fluid, comprising:
- an elongate body having a fluid admitting assembly and a fluid flow line configured to receive the fluid;
- a first crystal and a second crystal each having a face configured to be in contact with the fluid in the fluid flow line, wherein said first and second crystals have different refractive indices, different angles of incidence, or different refractive indices and different angles of incidence with respect to one another;
- at least one light source coupled to said first and second crystals and configured to direct light into said first and second crystals, said light having at least one wavelength, and said wavelength, said refractive indices and said angles of incidence being chosen such that said light undergoes total internal reflection at interfaces between said first and second crystals and the fluid;
- at least one light detector coupled to said first and second crystals configured to measure the reflected light exiting said crystals;
- and
- a processor coupled to said at least one light detector, said processor configured to determine attenuations of said light entering said crystals and configured to determine said refractive index of the fluid utilizing said attenuations, said refractive indices, and said angles of incidence of said crystals, wherein said refractive index is determined according to:
- A
- 1
- A
- 2
- =
- K
- 1
-
- d
- p
-
-
- 1
- K
- 2
-
- d
- p
-
-
- 2
- =
- h
-
- (
- η
- c
-
-
- 1
- ,
- Θ
- 1
- )
-
- [
- 1
- +
- (
- η
- c
-
-
- 2
- η
- s
-
- 1
- )
-
- (
- η
- f
-
- η
- m
- η
- M
-
- η
- m
- )
- 3
- /
- 2
- ]
- h
-
- (
- η
- c
-
-
- 2
- ,
- Θ
- 2
- )
-
- [
- 1
- +
- (
- η
- c
-
-
- 1
- η
- s
-
- 1
- )
-
- (
- η
- f
-
- η
- m
- η
- M
-
- η
- m
- )
- 3
- /
- 2
- ]
-
- η
- c
-
-
- 2
- η
- c
-
-
- 1
-
- sin
- 2
-
- Θ
- 2
-
- (
- η
- f
- /
- η
- c
-
-
- 2
- )
- 2
- sin
- 2
-
- Θ
- 1
-
- (
- η
- f
- /
- η
- c
-
-
- 1
- )
- 2
- ,
- wherein A1 is the attenuation of said first crystal and A2 is the attenuation of said second crystal, respectively, ηf is said refractive index of the fluid, ηc1 is the refractive index of said first crystal, ηc2 is the refractive index of said second crystal, Θ1 is the angle of incidence of said first crystal, Θ2 is the angle of incidence of said second crystal, ηM is a maximum refractive index value for said first and second crystals and is equal to 1.475 and ηm is a minimum refractive index value for said first and second crystals and is equal to 1.325, and ηs is a refractive index of a reference crystal material.
161 more elements
A method for determining the refractive index of a fluid, comprising:
- placing into a borehole traversing a formation a borehole tool having a fluid admitting assembly, a flow line, a first crystal and a second crystal each in contact with the fluid in the flow line, at least one light source, at least one light detector having signal processing circuitry associated therewith, and a processor, wherein said first and second crystals have different refractive indices, different angles of incidence, or different refractive indices and different angles of incidence with respect to one another;
- moving the fluid admitting assembly of the borehole tool into contact with the formation at a location of interest in the formation;
- causing formation fluid to flow into the flow line of the borehole tool and into contact with said first and second crystals;
- directing light from the at least one light source into said first and second crystals, and
- detecting with the at least one light detector the light exiting the crystals, said crystals and said light source having been chosen such that said light will undergo total internal reflection at interfaces between said crystals and said fluid;
- using the signal processing circuitry associated with the at least one light detector to compare the exiting light to an unattenuated light value for the light source associated with the at least one detector in order to obtain attenuation values;
- and
- determining with the processor the refractive index of the fluid flowing through the flow line using the attenuation values, the refractive indices, and the angles of incidence of said crystals, wherein the refractive index is determined according to:
- A
- 1
- A
- 2
- =
- K
- 1
-
- d
- p
-
-
- 1
- K
- 2
-
- d
- p
-
-
- 2
- =
- h
-
- (
- η
- c
-
-
- 1
- ,
- Θ
- 1
- )
-
- [
- 1
- +
- (
- η
- c
-
-
- 2
- η
- s
-
- 1
- )
-
- (
- η
- f
-
- η
- m
- η
- M
-
- η
- m
- )
- 3
- /
- 2
- ]
- h
-
- (
- η
- c
-
-
- 2
- ,
- Θ
- 2
- )
-
- [
- 1
- +
- (
- η
- c
-
-
- 1
- η
- s
-
- 1
- )
-
- (
- η
- f
-
- η
- m
- η
- M
-
- η
- m
- )
- 3
- /
- 2
- ]
-
- η
- c
-
-
- 2
- η
- c
-
-
- 1
-
- sin
- 2
-
- Θ
- 2
-
- (
- η
- f
- /
- η
- c
-
-
- 2
- )
- 2
- sin
- 2
-
- Θ
- 1
-
- (
- η
- f
- /
- η
- c
-
-
- 1
- )
- 2
- ,
- wherein A1 is the attenuation value of said first crystal and A2 is the attenuation value of said second crystal, ηf is said refractive index of the fluid, ηc1 is the refractive index of said first crystal, ηc2 is the refractive index of the second crystal, Θ1 is the angle of incidence of said first crystal, and Θ2 is the angle of incidence of said second crystal, ηM is a maximum refractive index value for said first and second crystals and equal to 1.475 and ηm is a minimum refractive index value for said first and second crystals and is equal to 1.325, and ηs is a refractive index of a reference crystal material.
163 more elements
Dependencies are inferred from the claim text.